The present invention relates to a defect inspecting method and a defect inspecting system for the inspection of defects existing on a substrate. Here, examples of the substrate are a semiconductor wafer and a mask used for the fabrication of a semiconductor device.
An inspecting apparatus or the like allows the detection of the defects that exist on the substrate such as the semiconductor wafer and the mask. Moreover, the use of an observing apparatus allows observing the details of the defects, collecting the observed images thereof, and analyzing the defects. In the defect inspecting system like this, the observing apparatus is required to be able to promptly execute the positioning as to where the defects detected by the inspecting apparatus exist on the substrate.
Conventionally, as a method of observing the defects on the substrate, there has been known the following method: The substrate as a whole or a portion thereof is inspected in advance so as to confirm whether or not the defects exist. Then, the positions of the defects thus found are stored as their coordinates on the substrate. Next, these stored coordinates are inputted into the observing apparatus through a communications member or a storage medium. Finally, based on the coordinates, the position-alignment is performed so that the defects will enter an observing field-of-view of the observing apparatus, then executing the observation.
At this occasion, if it is the case where the inspecting apparatus and the observing apparatus co-use the same substrate holding mechanism and substrate displacing mechanism and where the substrate remains held by the substrate holding mechanism at the time of transition from the inspection to the observation, simply displacing the observing field-of-view to the specified position-coordinates is enough for the position-alignment toward the observing apparatus. Accordingly, it is quite easy to permit the defects to enter the field-of-view.
In many cases, however, the inspecting apparatus requested to have a high throughput and the observing apparatus requested to have a high observing resolution are different apparatuses. Consequently, the easy position-alignment in the observing apparatus as described above is a difficult task. This requires the sharing of the coordinate system on the substrate by the inspecting apparatus and the observing apparatus through the use of some kind of method. Thus, for example, the following processing is executed: Positions of predetermined plurality of points on the substrate are detected using the inspecting apparatus and the observing apparatus. Then, the coordinate systems characteristic of the respective apparatuses are corrected based on this detection result, thereby causing the substrate coordinate system to be shared by both of the apparatuses.
As the concrete method therefor, there have been known the following methods, for example: A method in which the plurality of points provided along the circumference of the substrate and becoming a criterion of the positioning are constrained mechanically by the substrate holding mechanism, or a method in which an image of a predetermined pattern existing beforehand on the substrate is detected and the coordinate systems are corrected based on the position of this pattern.
JP-A-3-156947 has disclosed one example of the methods in which there is used the coordinate system that is common to a plurality of apparatuses including the inspecting apparatus and the observing apparatus.
In the above-described prior art method of mechanically constraining the points on the substrate, there exists a problem in the mechanical position reproducibility, i.e., the dimension accuracy. For example, it is difficult to implement the high-accuracy position-alignment at a level of micrometers.
Also, concerning the above-described method of correcting the coordinate systems in accordance with the detected pattern position, the method is inapplicable to, for example, the substrate before the pattern's formation of course. Moreover, when, for example, the inspecting apparatus is an optical type and the observing apparatus is an electron-beam type, i.e., the pattern detecting methods and the pattern detecting accuracies are different between both of the apparatuses, there exists the case where it is impossible to detect the same pattern in common to the apparatuses. Accordingly, the method is inapplicable to this case.
For example, when the substrate is covered with a transparent oxide-film and a pattern existing under the oxide-film is used for the position-alignment of the optical type inspecting apparatus, it is difficult to detect the pattern with the use of the electron-beam type observing apparatus.
JP-A-11-167893 has disclosed one example of the methods of detecting foreign substances in the case where the detecting methods are different between the inspecting apparatus and the observing apparatus. In this example, using both the coordinate values of the foreign substances on the substrate and the coordinate values thereof on the stage, it is intended to implement the sharing of the coordinate system between the inspecting apparatus and the observing apparatus. This makes it easier for the observing apparatus to find out the foreign substances that have been detected by the inspecting apparatus. Furthermore, the detected foreign substances are automatically selected depending on the characteristics such as the size, thereby enhancing the reliability of a correcting formula for the sharing of the coordinate system.
However, even if the inspecting apparatus and the observing apparatus employ the detecting methods similar to each other, when, for example, trying to observe into what form the defects detected at the time of the inspection have changed after the inspected substrate had been subjected to several processing steps, the pattern turns out to exist under a film formed at the processing steps. Consequently, it becomes impossible to detect the same pattern.